1. Field of the Invention
The invention concerns an x-ray detector of the type having a number of detector elements, each formed by a photodiode and a luminophore.
2. Description of the Prior Art
An x-ray detector of the above general type is known from “Digital Radiography with a Large-Area, Amorphous-Silicon, Flat-Panel X-Ray Detector System” by Spahn M. et al., Investigative Radiology 2000; Vol. 35, pages 260–266. In this known x-ray detector, a photodiode matrix (formed, for example, from amorphous silicon (a-Si)) is overlaid by a luminophore layer (formed, for example, from cesium iodide (Csl)). X-ray radiation radiated onto the luminophore layer is transduced into light in the luminophore layer. The light is detected with spatial resolution by the photodiode matrix and the resulting electrical signals are further processed by means of a downstream image-processing device.
In particular in radiography, it is sought for medical purposes to keep the dose of x-ray radiation radiated onto the person optimally low. For this, an apparatus is provided to regulate the dose rate. The apparatus includes a detector to measure the dose rate. The detector is connected via a regulation device with a high-voltage generator for the x-ray source. As soon as a predetermined dose has been reached, the high-voltage generator is deactivated by the regulation apparatus.
Conventionally, an ionization chamber disposed in the beam path is used as a detector to measure the dose rate. The structures formed by such detectors are disadvantageously imaged on the x-ray detector and undesirably adulterate the image information. In order to counteract this, a correction can ensue by means of computational methods. In specific cases, however, unwanted artifacts can occur in the implementation of such a correction. Conventional apparatuses to measure the dose are elaborate and, among other things, cause image errors.